The disclosure concerns a valve, in particular a solenoid valve, for controlling fluids, in particular hydraulic fluid, having a first port and a second port, a preliminary stage with a first valve seat and a first displaceable closing body, and a main stage with a second valve seat and a second displaceable closing body, wherein the second closing body has a passage opening to which the first valve seat is assigned.
Valves of the type cited initially are known from the prior art. In automobile construction, such valves are used for example in hydraulic brake systems in order to control the inlet or outlet of gasses or fluids, in particular brake fluid, or in order to control and regulate the flow direction. Widely varying systems are known from the field of vehicle brake systems, in which an active or partially active pressure build-up is achieved via a two-stage valve which has a preliminary or a main stage. Frequently, the valve is provided as a high-pressure switching valve, activation or operation of which opens a flow path between a master brake cylinder (primary circuit) and a pump element (secondary circuit). The two-stage configuration allows opening of the valve or clearance of the flow path even at high differential pressures. The primary circuit is connected to the first port and the secondary circuit to the second port, between which the two closing bodies are located. Usually a filter, in particular a radial filter, is assigned to the first port and serves to retain larger dirt particles which should not enter the primary circuit. When, because of the pressure conditions, the flow path extends from the second port to the first port, dirt particles are collected on the filter accordingly. When the pressure conditions change so that the flow path leads from the first port to the second port, the dirt particles are removed again and conducted in the direction of the preliminary stage. Since however the preliminary stage usually has a small stroke and a small flow opening, larger dirt particles may cause seizing or clogging of the preliminary stage, which can lead to a function loss of the valve.